1. Technical Field
The present invention relates to a printing apparatus and a printing method.
2. Related Art
Ink jet type printing apparatuses which perform printing on a medium by ejecting ink are known. Among such printing apparatuses, there are printing apparatuses which eject ink (UV ink) which is cured by the irradiation of light (for example, ultraviolet light (UV), visible light, or the like). In the printing apparatuses of this type, after UV ink is ejected from nozzles onto the medium, light is irradiated onto the dots which are formed on the medium. In this manner, the dots are cured and fixed to the medium (for example, refer to JP-A-2008-265285). For this reason, it is possible to form dots even with respect to a medium (for example, a film) which does not absorb ink.
In the printing apparatuses which eject the UV ink, there are cases where ultraviolet light is irradiated to the UV ink in two stages. In the first stage, the ultraviolet light is irradiated to the UV ink on the medium, whereby the wetting and spreading of the UV ink is controlled and the bleeding with the UV ink which is further ejected onto the medium thereafter is suppressed. In the second stage, ultraviolet light is irradiated such that the irradiation energy (integrated quantity of light) is stronger than the first stage, and the UV ink is completely cured. The first stage is sometimes called “pre-curing” or “pinning” and the second stage is called the “main curing”.
Yellow UV ink absorbs ultraviolet light more easily than cyan or magenta UV inks. For this reason, during the pre-curing which irradiates ultraviolet light with comparatively weak irradiation energy, ultraviolet light is absorbed at the surface of the yellow ink and the ultraviolet light may not reach the inner portion of the yellow ink. In such a case, only the surface is cured and the inner portion enters a state of having fluidity. When ultraviolet light is irradiated with strong irradiation energy to the yellow ink in this state and the main curing is performed, wrinkles are generated in the surface (the surface which has already been cured) due to the yellow ink of the inner portion undergoing curing shrinkage.
In addition, in a case where a polymerizable compound includes one type or two or more types which are selected from a group consisting of acrylate 2-(2-vinyloxyethoxy)ethyl, 3-oxa-5-hexene-1-ol, phenoxyethyl acrylate, 4-hydroxybutyl acrylate, tricyclodecane dimethylol diacrylate, dipentaerythritol hexaacrylate, and ethoxylated isocyanurate triacrylate, wrinkles are remarkably generated. In particular, in a case where the components of the yellow UV ink include acrylate 2-(2-vinyloxyethoxy)ethyl, wrinkles are remarkably generated. Since there is no inhibition of polymerization by moisture or bases and there is no polymerization inhibition by oxygen in acrylate 2-(2-vinyloxyethoxy)ethyl, the effect is more effective, whereby the above-described problem is more remarkably generated.
In addition, in a case where the components of the yellow UV ink include one type or more of pigment consisting of C. I. Pigment Yellow 150, 155, and 180, the wrinkles are even more remarkably generated.